tailieunhanh - Preconcentration and spectrophotometric determination of anionic surfactants in water byflow injection analysis and solid phase ion-pair extraction

A new automated procedure for preconcentration and analysis of anionic surfactants in water using solid-phase extraction (SPE) in a flow injection (Fl) system together with an UV-vis detection is reported in this paper. The method involves extraction of blue coloured ion-pair complex of anionic surfactants and methylene blue into solid phase and their elution from the SPE column with organic solvent (chloroform stabilised with methanol) and subsequent measurement in an UV-vis flow cell at 650 nm. The system is well optimised before to apply for analysis of real samples. The advantages of the developed method are presented. The system can be used for analysis of anionic surfactants at the ng/mL range. | Journal of Chemistry Vol. 43 2 P. 253 - 257 2005 PRECONCENTRATION AND SPECTROPHOTOMETRIC DETERMINATION OF ANIONIC SURFACTANTS IN WATER By FLOW INJECTION ANALySIS AND SOLID PHASE ION-PAIR EXTRACTION Received 7iti-May-2004 LE THANH HAI Institute for Environment and Resources VNU of Hochiminh City SUMMARY A new automated procedure for preconcentration and analysis of anionic surfactants in water using solid-phase extraction SPE in a flow injection Fl system together with an UV-vis detection is reported in this paper. The method involves extraction of blue coloured ion-pair complex of anionic surfactants and methylene blue into solid phase and their elution from the SPE column with organic solvent chloroform stabilised with methanol and subsequent measurement in an UV-vis flow cell at 650 nm. The system is well optimised before to apply for analysis of real samples. The advantages of the developed method are presented. The system can be used for analysis of anionic surfactants at the ng mL range. INTRODUCTION For analysis of anionic surfactants various techniques have been applied such as extraction 1 paper 2 and thin-layer chromatography 3 electrophoresis 4 ion-exchange chromatography 5 gas chromatography 6 HPLC 7 . Among the methods for determination of anionic surfactants in water as found in literature the methylene blue ion-pair extraction method is the most common and generally used as described in ISO 7875-1 and standard methods for the examination of water and waste water 8 . Almost all spectrophotometric methods for the determination of anionic surfactants in water samples are based on liquid -liquid extraction. These methods however are still not automated sometime are time-consuming and the detection limit LOD obtained were not as high as required for low level analysis which is a requirement of environmental monitoring. Flow injection analysis FIA has become a useful tool for automation of analysis procedures involving complex sample treatment. Furthermore